In Assassin’s Creed: Brotherhood for the PS3, Xbox 360, and PC, you can unlock several items by completing the shop quests from the different shops in the game.
Captain’s Sword – Complete the Faith shop quest from the Blacksmith
Fast Poison – Complete the Venomous shop quest from the Doctor
Large Quiver – Complete the Pulling Threads shop quest from the Tailor
Seusenhofer Chest Guards – Complete the Exotica shop quest from the Blacksmith
Seusenhofer Pauldrons – Complete the Exotica shop quest from the Blacksmith
Spada Lunga – Complete the Blood Money shop quest from the Blacksmith
Vaticano Treasures Map – Complete the Trendsetting shop quest from the Art Merchant